Light availability interferes with absorption and translocation of 14 C-glyphosate in Urochloa brizantha cv. Marandu pla
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Light availability interferes with absorption and translocation of 14C‑glyphosate in Urochloa brizantha cv. Marandu plants Larissa Martins Mota1 · Kassio Ferreira Mendes1,2 · Lucas Heringer Barcellos Júnior1 · Elisa Maria Gomes da Silva1 · Ivan Ferreira Furtado1 · Valdemar Luiz Tornisielo2 Received: 29 May 2020 © Akadémiai Kiadó, Budapest, Hungary 2020
Abstract This research aimed to evaluate the absorption and translocation of 14C-glyphosate in Urochloa brizantha cv. Marandu subjected to different light availabilities. Six light conditions were studied: application followed by 24, 48 or 72 h of dark, 72 h of light, 24 h of dark + 48 h of light and daytime in different evaluation times: 0, 3, 6, 12, 24, 48, and 72 h after application of 14C-glyphosate (1.67 kBq/plant). The herbicide absorption was higher in plants with less light availability at 72 HAA (48 and 21% for 72 h of darkness and 72 h of light, respectively); however, there was a greater translocation of 14C-glyphosate to roots in the high availability of light (23 and 5% for 72 h of light and 72 h of dark, respectively). Thus, in U. brizantha plants, under conditions of greater light availability, 14C-glyphosate was less absorbed, but the product was more translocated. It is recommended that farmers to apply glyphosate at daytime since the light positively favored translocation, which is essential to the herbicidal activity. Keywords Application schedule · Application technology · Nighttime application · Application timing
Introduction Glyphosate (N-(phosphonomethyl)glycine) enzyme inhibitor 5-enolpyruvylshikimate-3-phosphate synthase (EPSPs), used in weed chemical control, is considered the most important herbicide worldwide [1], being registered in more than 130 countries with 150 distinct trademarks, proving effective in controlling more than 300 weed species and used in more than 100 agricultural crops [2, 3]. The EPSPs inhibitor herbicide is mainly absorbed by the aerial part of the plant since when applied to the soil, it is strongly adsorbed [4]. Some factors affect herbicide absorption, such as the cuticular layer on the surface of leaves, which is considered the greatest barrier to absorption; in addition, the increase in soil moisture tension, which occurs with soil drying, can strongly reduce the absorption of the product by plants [5].
* Kassio Ferreira Mendes [email protected] 1
Federal University of Viçosa, Viçosa, MG, Brazil
University of São Paulo, Piracicaba, SP, Brazil
2
Under favorable conditions, glyphosate penetrates the leaves, then reaches the roots, rhizomes, and apical meristems, by translocation via phloem and xylem [6]. The negative charges of the cell wall and plasmalemma repel the herbicide, which is strongly anionic, contributing to the movement of glyphosate in the apoplast [7]. However, the phloem are the main transport mechanism of herbicides applied in the post-emergence of weeds [8]. Absorption and translocation are fundamental to reach the site of action and represent an essential factor in the efficacy of
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